Apparatus for recovering zinc from zinciferous material containing iron



May l5, 1951 F. F. POLAND 2,552,648

APPRWS FOR RECOVERING ZINC m0 ZINCIFERUS' ATERIL CONTINING IRON' Original Filed Sept. 6, 1945 2'Shqts-Shest 1 F2 migra) (12% 0 bgymw @www May 15, 1951 FfmPoLANn 2,552,648

' APPARATUSFOR RECOYERING ZINC FROH-ZINCIFERDUS MATERIAAL CONTAINING IRON.

Original Filed Sept. 6; 1945 2 Sheets-Sheet 2 Patented May 15, .1951

VAPPARATUS FOR RECOVERING ZINC FROM ZINCIFEROUS MATERIAL CONTAINING YIRON Frank -F. Poland, Rome, N. Y.,-assignortoRevere Copper Aand Brass Incorporated, `Rome,'N. Y., a corporation of Maryland Original application September 6, 1945,'Serial No.

614,619. Divided and this application November 6, 1948, Serial No. 58,734

(Cl. 26S- 16) 3 Claims. 1 lMy invention relates-to apparatus for recovering zinc from zinciferous material containing iron, this application being a divisionof-*my copending application Serial Number 614,619, filed September 6, 1945,r now U. S. Patent 2,463,468.

iron and zinc.

off.

zinc.

upper surface.

metallic zinc.

of the pool.

to apoint suflicientto melt the residue, sayabout 2750 whereupon "it is vtapped from the lfurnace toclear the latter Yof the same. Uponsuch removal `of the residue the above described cycle of operations may berepeated. In-this Way it is `If the dross werelheated to such This percentage decrease As shown, the

In the hot galvanizing of iron to produce,for possible .torecover better than 95% ofthe Zinc example, galvanized yiron 'sheets the iron sheet contained in the drosscharged to the furnace. after being coated with a suitable flux is dipped 4In the above example of Vthe practice `of the into a bath of molten zinc. The small amount of method, it will be observed that for performing IOn flOm each Sheet iS dSSOlVEd by the liquid `l the Kevaporating operation lthe temperature of Zinc and forms an ntelmetalli @Ompound yof the molten dross is raised to apoint less than This compound floats on the top the melting point of the residue so as to mainof the bath and is from time to time skimmed tain `the latter in solid .condition and cause it Such skimmings, which are vcommonly to sink, witnthe result that the'rmaterial'adtermed zinc dross, have a melting point of jacent the surface of the pool-contains a maxiabout 1300 F. as comparedftoabout 790 F. for mum of zinc.

The compositions of the skimmings vary, temperature as would cause the iron constitubut in general they contain about 6% iron, and ent to be continually in molten condition, -not usually impurities such as lead that may be preonly would an increased energy input to the fursent in the bath. A vtypical analysis of the nacebe necessary and the furnace liningfdeteriorskimmings is iron 6%, leadV 1%, zinc balance. aterapidly, 'but the molten constituents of the According to a preferred Way of practising the pool would `contain a progressively decreasing present invention, the zinc dross is melted and percentage of zinc. charged into a furnace chamber to form therein would cause a progressive decrease in the rate of a rather deep pool having an extensive free zinc evaporation andfmake it necessary to clear The pool is then lheated in this the furnace chamber from time -to time of dross chamber under non-oxidizing conditions, prefwhich in the aggregate would contain a large erably by heat radiated downwardly on its free amount of zinc, with the net result of' such costly surface, to raise its temperature sufficiently to and otherwise uneconomical operation as to be cause zinc to be evaporated therefrom While reimpractical. It has been found that heating the taining the iron and lead contents of the dross. dross to a temperature of about 1700 to 2000 F. These zinc vapors are conducted from `thefurfor performing-the evaporating operation will senace, preferably to a zinc condenser-where they curebest results in respect to satisfactory and are cooled to precipitate them as liquid zinc, economic operation. which latter may from time to time to tapped The accompanying drawings show a preferred from the kcondenser and cast to lform slabs of embodiment of apparatus for use in practising As vthe vaporizing operation prothe invention. ceeds the molten dross quickly becomes -`satur- In "these drawings: ated with the iron content which separates out Fig. 1 is a section on the line vl-I of Fig. 2, as a solid and sinks as a residue to the lbottom Withparts in elevation;

Fresh molten dross is chargedinto Fig. 2 is a section on the line 2-2 of Fig. 1; the chamber from time to time until such :acand cumulation of the residue occurs as to Warrant Figs.'3 and 4 are, respectively, sections on the its removal. This residue, which consists of about lines -3-3 and 4--4 o-f Fig. 2. 85% iron admixed with zinc, or admixed with 45 As illustrated in the-drawings, the furnace has zinc-lead alloy if lead is present in the dross, a lower body portion which comprises a metallic has an extremely high melting point in the neighcasing I, and a removable cover portion which borhood of 2600a F. It strongly adheres 13o-the comprises a metallic casing 3. bottom and side walls of the furnace chamber, casing I is provided adjacent its upper edge with and cannot be removed by mechanical means a horizontal flange 5 which extends continuwithout considerable difliculty and destructive inously about the Afour sides of the casing, this jury to the expensive furnace lining and withflange carrying spaced upwardly extending verout first cooling down andopening the furnace. tical flanges l which likewisey extend continuously To remove the residue, according to-the present about the four sides of the casing. The casing invention the temperature of the furnace is raised 55 3 of the cover portionof the furnace is provided with an outwardly extending bracket or flange 9 extending continuously about the four sides of said casing. This bracket carries a channelshaped member II having downwardly extending webs I3 and a central downwardly extending flange I5, the member II and flange I likewise extending continuously about the casing. As clearly illustrated in Fig. 2, the upwardly extending flanges 1 are received in the spaces between the flange I5 and webs I3. The spaces between the flanges 1 and that portion of the casing I which is above the flange 5 may be filled with oil or sand, into which project the flange I5 and. that web I3 which is adjacent the casing. In this way a labyrinth seal is formed to exclude air from the two casings when the cover is in place.

The furnace chamber I1 is shown as provided with a lining I9, which lining may be of suitable refractory material such as silicon carbide, claygraphite mixture, or the like. The lining, as shown, is supported and backed by a filler 2| which may be formed of refractory firebrick.

As illustrated, the opposite side walls of the ylining I9 are formed to provide shelves 23 near the top of the furnace chamber. On these shelves rest blocks 25 of heat refractory electric insulating material such as aluminum oxide A1203, On these blocks are supported plates '21 of electric conductive material such as graphite. Extending between the plates at opposite sides of the furnace chamber in secured relation to said plates are heating resistors 29 which also may be formed of graphite, the arrangement being such that the plates 21 connect the resistors for series flow of current through them. As shown, the resistors at the ends of the row of resistors are connected to extensions 3l leading through openings 33 in the furnace Walls, in electric insulated relation thereto, to the exterior of the casing the extensions at the exterior of the casing being provided with terminals 35 for connection to the source of energizing current for the resistors.

Resting on the top of the lining I9 and extending transversely across the furnace are shown lapped slabs 31, preferably formed of graphite, which act to reflect heat downwardly. Resting on the furnace roof formed by these slabs is a layer 39 of insulating material, preferably granulated carbon.

The casing 3 of the removable cover of the furnace, as shown, contains a central arch 4I, of refractory material, resting on abutments 43 of such material, the latter being retained in the casing 3 by the flanges l5 secured thereto and extending about the four sides of the casing interiorly thereof adjacent its lower edge.

As shown, leading through the walls of the furnace chamber is a conduit 41 for discharging zinc vapors to a condenser fil, the condenser being provided with a vent 5i having therein an adjustable damper or valve 53 for regulating the pressure in the condenser and furnace chamber.

For charging the furnace chamber with the molten Zinc dross the casing I is provided with an extension 55 in which is contained a body of firebrick or the like built up to form a funnel 51 into which the molten dross may be poured from a ladle. The discharge opening 59 of the funnel leads to an interior chamber 6I formed in the body of firebrick. This chamber is divided into two compartments by a slab 3, of refractory material, extending from the top of the chamber to adjacent its bottom 65 so asV to form beneath the slab a passage 61. Leading from thecompartment at the right of the slab 63 as viewed in Fig. 2 is a passage 69 which extends through the furnace walls and opens into the furnace chamber Well above its bottom. In operation, when the molten dross is poured into the funnel 51 it will discharge into the furnace chamber through the passage 69 to l-Ill the same to the desired level. When the pouring operation is discontinued there Will remain in the chamber EI a pool of material the upper level B of which is determined by the height of the passage 69 above the bottom 65 of the chamber. As the slab 63 projects into this pool the latter seals the passage 69 from the atmosphere,

Suitable heating means are provided for preventing the molten zinc dross in the compartment at the left of the slab 63 as viewed in Fig. 2 from freezing when the pouring operation is discontinued. This heating means, in the embodiment of the invention illustrated, com- .prises a torch 1I adapted to project a iiame into such compartment, the torch, as shown, being provided with a combustible gas supply connection 13 and an air supply connection 15 respectively leading to sources of gas and air under pressure. The flame may be regulated by the valves 11 in these connections. Conveniently the chamber 6I is provided with a port 19 for igniting the gas and air mixture. The products of combustion from the flame will escape from the chamber through the passage 59 and funnel 51 to the atmosphere.

In operation, the furnace chamber I'I may be filled With molten zinc dross in the way above described to a level A. Sufcient current may be passed through the resistors to radiate heat downwardly from them and the roof slabs 31 of the furnace chamber to heat the surface portion of the pool to a temperature of about 1700 to 2000 F. which will cause zinc rapidly to evaporate from such surface and pass through the conduit 41 into the condenser 49 where the zinc vapors will condense into liquid zinc and collect at the bottom of the condenser. From time to time the molten zinc may be discharged from the condenser through the normally plugged tap 8l and cast into slabs.

From time to time additional molten zinc dross may be charged into the furnace chamber until there accumulates at the bottom of the chamber a mass of the residue up to say the level C, whereupon the current fiowing through the heating resistors may be increased to raise the contents of the furnace to about 2150" F. for melting such accumulation. When molten this accumulation may be discharged from the furnace chamber through the normally plugged tap 83.

In practice, but Without limitation thereto, the furnace chamber may be about l1/3 feet wide and 9 feet long so as to cause the pool of molten dross therein to present a free upper surface of considerable area. The molten dross may initially fill the chamber to a depth of about 24 inches, and when the accumulated residue fills the bottom portion of the chamber to a depth of about 18 inches that residue may be melted and discharged from the furnace chamber.

The passage 99 is preferably of such bore and length that no appreciable vaporization of zinc will occur in the compartment of the chamber 6I at the right of the slab 63 as viewed in Fig, 2, 0r at least insufficient vaporization to cause the iron content of the dross to separate out in that compartment. The material in the compartment just mentioned will be maintained in molten condition by heat conducted from the compartment at the left of the slab 63 as viewed in Fig. 2 and by heat passing from the furnace chamber through the passage 59. Satisfactory results will be secured with a furnace chamber of the dimensions above mentioned when the passage t9 is about a inches in diameter and 30 inches long.

It will be understood that the zinc dross is treated in the furnace chamber under non-oxidiz ing conditions to prevent oiiidization of the Zinc vapors. For initially clearing the chamber of air, conduits 85 of refractory material, such as silicon carbide or graphite, extending from the exterior of the furnace through the furnace walls and discharging into the furnace chamber may be provided. lThese conduits may communicate with a pipe 81 leading to a suitable source of nitrogen under pressure, the supply of nitrogen passing through the conduits 85 being controlled by the stop valves 89. 53 is so adjusted as to maintain the furnace chamber at just above atmospheric pressure so as to insure against leakage of air into said chamber.

It will be understood that within the scope of the appended claims wide deviations may be made from the steps of the method and embodiment of the apparatus described without departing from the spirit of the invention.

I claim:

1. Apparatus for treating molten material comprising means forming a furnace chamber, means for heating said furnace chamber, means for entering molten material into said furnace chamber comprising a pair of compartments at the exterior of said chamber, which compartments are separated by a common dividing wall and one of which is closed to the atmosphere, a passage leading from a point above the bottom of the last mentioned compartment to the furnace chamber for conducting molten material from said compartment to said chamber, a passage open to the atmosphere for receiving and charging molten material into the other compartment at a point above the bottom of that compartment, a passage in said dividing Wall placing the two compartments in communication at a point adjacent their bottoms for causing flow of molten material from the compartment to which said material is charged to the compartment closed f to the atmosphere, which last mentioned passage constitutes the sole means of communication between said compartments; and heating means, other than the means for heating the furnace chamber, for the compartment to which such material is charged for maintaining the material trapped in that compartment in molten condition between charging operations.

2. Apparatus for treating molten material comprising means forming a furnace chamber, means for heating said furnace chamber, means for entering molten material into said furnace chamber, the last mentioned means comprising walls forming a chamber at the exterior of said furnace chamber, which chamber formed by said walls is separated into two compartments by an imperforate dividing wall extending downward from the top of such chamber to adjacent its bottom so as to form an opening connecting the two compartments adjacent their bottoms and preventing communication between said compartments other than by way of such opening,

Preferably, the damper a passage placing one of said compartments at a point above said opening in communication with said furnace chamber, means presenting a charging port in communication with the atmosphere for receiving and entering the molten material into the other of said compartments at a point also above said opening; and heating means, other than the means for heating the furnace chamber, for the compartment with which said charging port communicates for maintaining the material trapped in that compartment in molten condition between charging operations and for causing heat to be conducted through said dividing wall to the material in the other compartment for acting to keep it also in molten condition between charging operations.

3. Apparatus for evaporating zinc from molten zinciferous material comprising means forming a substantially closed furnace chamber, means for heating the contents of said furnace chamber for evaporating zinc from such contents and for conducting the evaporated Zinc in vapor form from said chamber, means for entering the molten material into said furnace chamber comprising a first compartment at the exterior of said chamber closed to the atmosphere, a passage leading from a point above the bottom of said compartment to the furnace chamber for conducting the molten material from said compartment to said chamber, which passage is elongated to reduce the heating of the molten material in said compartment by heat conducted through said passage from the furnace chamber to said compartment so as to prevent material evaporation of zinc from such material in said compartment, means forming a second compartment having a wall common to both compartments for separating the two, which second compartment has a charging opening communicating with the atmosphere for entering the molten material into it, a passage in said wall placing the two compartments in communication for causing flow of the molten material from said second compartment to said rst compartment, which last mentioned passage constitutes the sole means of communication between said compartments and opens into said first compartment at a point below that at which the passage leading from said first compartment to the furnace chamber communicates with said first compartment and opens into said second compartment at a point below that at which said charging opening communicates with said second compartment; and heating means, other than the means for heating the furnace chamber, for said second compartment for maintaining the material trapped in that compartment in molten condition between charging operations.

FRANK F. POLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,333,721 Johnson Mar. 16, 1920 1,938,582 Davis Dec. 12, 1933 2,156,420 Anderson et al May 2, 1939 2,429,584 Poland Oct. 21, 1947 

